Biology subjects

Amiri, B.

Publications and source records attributed to Amiri, B..

4 recordsLinked to original sources

bioRxiv2023

Host tracheal and intestinal microbiomes inhibit Coccidioides growth in vitro

Coccidioidomycosis, also known as Valley fever, is a disease caused by the fungal pathogen Coccidioides. Unfortunately, patients are often misdiagnosed with bacterial pneumonia leading to inappropriate antibiotic treatment. Soil bacteria B. subtilis-like species exhibits antagonistic properties against Coccidioides in vitro; however, the antagonistic capabilities of host microbiota against Coccidioides are unexplored. We sought to examine the potential of the tracheal and intestinal microbiomes to inhibit the growth of Coccidioides in vitro. We hypothesized that an uninterrupted lawn of microbiota obtained from antibiotic-free mice would inhibit the growth of Coccidioides while partial in vitro depletion through antibiotic disk diffusion assays would allow a niche for fungal growth. We observed that the microbiota grown on 2xGYE (GYE) and CNA w/ 5% sheeps blood agar (5%SB-CNA) inhibited the growth of Coccidioides, but that grown on chocolate agar does not. Partial depletion of the microbiota through antibiotic disk diffusion revealed that microbiota depletion leads to diminished inhibition and comparable growth of Coccidioides growth to controls. To characterize the bacteria grown and narrow down potential candidates contributing to the inhibition of Coccidioides, 16s rRNA sequencing of tracheal and intestinal agar cultures and murine lung extracts was performed. The identity of host bacteria that may be responsible for this inhibition was revealed. The results of this study demonstrate the potential of the host microbiota to inhibit the growth of Coccidioides in vitro and suggest that an altered microbiome through antibiotic treatment could negatively impact effective fungal clearance and allow a niche for fungal growth in vivo. ImportanceCoccidioidomycosis is caused by a fungal pathogen that invades host lungs, causing respiratory distress. In 2019, 20,003 cases of Valley fever were reported to the CDC. However, this number likely vastly underrepresents the true number of Valley fever cases as many go undetected due to poor testing strategies and lack of diagnostic models. Valley fever is also often misdiagnosed as bacterial pneumonia, resulting in 60-80% of patients being treated with antibiotics prior to accurate diagnosis. Misdiagnosis contributes to a growing problem of antibiotic resistance and antibiotic induced microbiome dysbiosis, and the implications on disease outcome are currently unknown. 5%-10% of symptomatic Valley fever patients develop disseminated and/or chronic disease. Valley fever causes a significant financial burden and reduced quality of life. Little is known regarding what factors contribute to the development of chronic infection and treatments for disease are limited.

microbiology↗

bioRxiv2022

On multistability and constitutive relations of cell motion on Fibronectin lanes

Cell motility on flat substrates exhibits multistability between steady and oscillatory morphodynamics, spread and moving states, the biphasic adhesion-velocity relation, and the universal correlation between speed and persistence (UCSP) as simultaneously observed phenomena. Their universality and concurrency suggest a unifying mechanism to exist causing all of them. We search for that mechanism by investigating trajectories of MDA-MB-231 cells on Fibronectin lanes. We also find multistability caused by the clutch mechanism of retrograde flow. Control of the clutch parameters by integrin signalling causes the biphasic adhesion-velocity relation. Protrusion competition based on the clutch causes direction reversal events, the statistics of which explains the UCSP. We suggest that F-actin polymerisation, clutch mechanism of retrograde flow, protrusion competition via membrane tension and drag forces cause the multistability and dynamic cell states, state transition statistics causes the UCSP and the control of this dynamic system by integrin signalling entails the adhesion-velocity relation.

biophysics↗

bioRxiv2021

Computational toolbox for ultrastructural quantitative analysis of filament networks in cryo-ET data

A precise quantitative description of the ultrastructural characteristics underlying biological mechanisms is often key to their understanding. This is particularly true for dynamic extra- and intracellular filamentous assemblies, playing a role in cell motility, cell integrity, cytokinesis, tissue formation and maintenance. For example, genetic manipulation or modulation of actin regulatory proteins frequently manifests in changes of the morphology, dynamics, and ultrastructural architecture of actin filament-rich cell peripheral structures, such as lamellipodia or filopodia. However, the observed ultrastructural effects often remain subtle and require sufficiently large datasets for appropriate quantitative analysis. The acquisition of such large datasets has been enabled by recent advances in high-throughput cryo-electron tomography (cryo-ET) methods. However, this also necessitates the development of complementary approaches to maximize the extraction of relevant biological information. We have developed a computational toolbox for the semi-automatic quantification of filamentous networks from cryo-ET datasets to facilitate the analysis and cross-comparison of multiple experimental conditions. GUI-based components simplify the manipulation of data and allow users to obtain a large number of ultrastructural parameters describing filamentous assemblies. We demonstrate the feasibility of this workflow by analyzing cryo-ET data of untreated and chemically perturbed branched actin filament networks and that of parallel actin filament arrays. In principle, the computational toolbox presented here is applicable for data analysis comprising any type of filaments in regular (i.e. parallel) or random arrangement. We show that it can ease the identification of key differences between experimental groups and facilitate the in-depth analysis of ultrastructural data in a time-efficient manner.

cell biology↗

bioRxiv2019

Lamellipodin tunes cell migration by stabilizing protrusions and promoting adhesion formation

Efficient migration on adhesive surfaces involves the protrusion of lamellipodial actin networks and their subsequent stabilization by nascent adhesions. The actin binding protein lamellipodin (Lpd) is thought to play a critical role in lamellipodium protrusion, by delivering Ena/VASP proteins onto the growing plus ends of actin filaments and by interacting with the WAVE regulatory complex (WRC), an activator of the Arp2/3 complex, at the leading edge. Using B16-F1 melanoma cell lines, we demonstrate that genetic ablation of Lpd compromises protrusion efficiency and coincident cell migration without altering essential parameters of lamellipodia, including their maximal rate of forward advancement and actin polymerization. We also confirmed lamellipodia and migration phenotypes with CRISPR/Cas9-mediated Lpd knockout Rat2 fibroblasts, excluding cell type-specific effects. Moreover, computer-aided analysis of cell edge morphodynamics on B16-F1 cell lamellipodia revealed that loss of Lpd correlates with reduced temporal protrusion maintenance as a prerequisite of nascent adhesion formation. We conclude that Lpd optimizes protrusion and nascent adhesion formation by counteracting frequent, chaotic retraction and membrane ruffling. Summary statementWe describe how genetic ablation of the prominent actin- and VASP-binding protein lamellipodin combined with software-aided protrusion analysis uncovers mechanistic insights into its cellular function during cell migration.

cell biology↗